firepower 68 Posted October 30, 2009 Report Share Posted October 30, 2009 We all understand the principle of a moderator. By allowing the expansion of the explosive gasses and releasing them relatively slowly the blast from the explosion is diminished. Using ammunition that is subsonic completes the picture and the bang becomes a "phut" in the case of .22 or in the case of hypersonic ammunition and larger calibres a "whoosh" So why does my .17hmr produce a resounding crack? The velocity of a .17hmr is around 2600 fps out at the muzzle, this is a similar velocity to the .308 the .308 that produces a far bigger blast at the end of the barrel and is also hypersonic but it is still quieter as it exits the moderator. Is this due to the fact that all of the larger calibres have specific moderators? As opposed to the .17hmr which always seem to have moderators that are originally for the .22. The SAK mod is even stamped .17hmr/.22 Surely the escaping gasses from an oversized bore in the moderator must contribute to the “crack†Does any company actually make a specific .17hmr moderator ? Quote Link to post
RicW 67 Posted October 31, 2009 Report Share Posted October 31, 2009 We all understand the principle of a moderator. By allowing the expansion of the explosive gasses and releasing them relatively slowly the blast from the explosion is diminished. Using ammunition that is subsonic completes the picture and the bang becomes a "phut" in the case of .22 or in the case of hypersonic ammunition and larger calibres a "whoosh"So why does my .17hmr produce a resounding crack? The velocity of a .17hmr is around 2600 fps out at the muzzle, this is a similar velocity to the .308 the .308 that produces a far bigger blast at the end of the barrel and is also hypersonic but it is still quieter as it exits the moderator. Is this due to the fact that all of the larger calibres have specific moderators? As opposed to the .17hmr which always seem to have moderators that are originally for the .22. The SAK mod is even stamped .17hmr/.22 Surely the escaping gasses from an oversized bore in the moderator must contribute to the “crack†Does any company actually make a specific .17hmr moderator ? Interesting question, as proved by the fact that no-one can give a sensible answer! My guess would be that the tiny bullet fired from HMR generates a high pitched sonic "boom", while the bigger .22cf and heavier calibre bullets produce a lower frequency sound. The human ear percieves lower frequency sounds as quieter than high frequency, although the energy levels may be the same. A two stroke motor bike sounds "louder" than a four stroke at the same decibel level. The sonic boom from Concorde was deeper than that from a fighter plane, On a point of information, no bullet is "hypersonic". Ignore the daft names given by ammo makers. "hypersonic" means travelling at more than 5 times the speed of sound. 5625 fps? I think not! If I am correct on this then the reason no-one makes a dedicated HMR mod is that it would make damn-all difference to the percieved sound. Ric Quote Link to post
SNAP SHOT 194 Posted October 31, 2009 Report Share Posted October 31, 2009 There is a company that do make a dedicate mod. for the hmr. but i cannot for the life of me remember it's name. What i do know is it's very small ans is retailing at around 130 quid... Snap. Quote Link to post
jamie g 17 Posted October 31, 2009 Report Share Posted October 31, 2009 There is a company that do make a dedicate mod. for the hmr. but i cannot for the life of me remember it's name. What i do know is it's very small ans is retailing at around 130 quid... Snap. yes its uk custom shop owned by andrew banner. also dm80 does the same. and john bokket can do it also Quote Link to post
CharlieT 32 Posted October 31, 2009 Report Share Posted October 31, 2009 There is a company that do make a dedicate mod. for the hmr. but i cannot for the life of me remember it's name. What i do know is it's very small ans is retailing at around 130 quid... Snap. It's LEI (Law Enforcement International). The smallest dedicated HMR mod. Distributed by Edgar Bros. As you say priced around £130. Quote Link to post
SNAP SHOT 194 Posted October 31, 2009 Report Share Posted October 31, 2009 There is a company that do make a dedicate mod. for the hmr. but i cannot for the life of me remember it's name. What i do know is it's very small ans is retailing at around 130 quid... Snap. It's LEI (Law Enforcement International). The smallest dedicated HMR mod. Distributed by Edgar Bros. As you say priced around £130. thats the one mate, i couldn't remember it for the life of me... lol its a fantastic looking bit of gear they also make one the the .22lr very flashy Snap. Quote Link to post
RicW 67 Posted November 2, 2009 Report Share Posted November 2, 2009 Ah Well. So much for theory . . . Ric Quote Link to post
firepower 68 Posted November 3, 2009 Author Report Share Posted November 3, 2009 (edited) Thanks for the help chaps, lets see how quiet it will be with a new mod Edited November 3, 2009 by firepower Quote Link to post
madsarmy 0 Posted November 4, 2009 Report Share Posted November 4, 2009 I can recommend the Wildcat Whisper (UK Custom Shop). Over barrel design. Easy to strip & clean. Very well engineered. Quote Link to post
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